A III-V group nitride semiconductor has been variously used for an optical device such as blue/green LEDs (light emitting diodes), a high speed switching device such as a MOSFET (metal semiconductor field effect transistor) and a HEMT (hetero junction field effect transistor), a light source of an illumination or a display apparatus, and the like. In particular, a light emitting device using a III group nitride semiconductor has a direct transition-type bandgap corresponding to the range of visible rays to ultraviolet rays, and can perform high efficient light emission.
The nitride semiconductor has been mainly utilized as a LED or a LD (laser diode), and research for improving the manufacturing process or light efficiency had been conducted.